Hello, I'm Jewel with Kingston Technical Support and would like to offer our assistance. If used in an Android 4.1 or later phone, you may have been affected by a known issue that caused different microSDHC cards to stop being recognized as you described. This issue has since been resolved within our microSDHC cards and as we stand by all our products the card can be replaced under it's lifetime warranty. Please call us at 1-800-435-0640 (USA and Canada only) M - F 6am - 6pm PT and I or another available Technician will assist you. Please be sure to have the part in question on hand when you call.
Thank you for selecting Kingston as your upgrade partner.